Breast cancer and sex steroids: critical review of epidemiological, experimental and clinical investigations on etiopathogenesis, chemoprevention and endocrine treatment of breast cancer

Palladium(II)-Catalyzed Tandem γ-C(sp2)-H Arylation and Cyclization for the Construction of Natural Product-Like Polycyclic Fused ortho-Quinone Scaffolds

Here, we report a novel strategy for the direct construction of polycyclic fused ortho-quinone scaffolds through palladium(II)-catalyzed tandem γ-C(sp2)-H arylation and cyclization of arylglyoxals with aryl iodides. This transformation features unique tandem transient directing of γ-C(sp2)-H arylation and cyclization reaction mode, broad substrate scope, especially for the aromatic substrates containing oxygen and sulfur atoms, and avoiding the common issue of aromatization due to the construction of the hexatomic ring.

The apoptotic effects of progesterone on breast cancer (MCF-7) and human osteosarcoma (MG-636) cells

Purpose

Progesterone has been reported to inhibit the proliferation of breast cancer and osteosarcoma cells; however, its inhibitory mechanism has not yet been clarified. The aim of the present study was to clarify the effects of progesterone on apoptosis in breast cancer (MCF-7) and human osteosarcoma (MG-63) cells.

Materials and methods

In this experimental study the cytotoxic effect of progesterone was measured in MCF-7 and MG-63 cells exposed to different concentrations of progesterone using MTT assay, and effective concentrations were identified. The expression levels of the Bax, P53 and Bcl-2 genes were evaluated by real-time PCR, and caspase-3, 8 and 9 activity levels were determined using a colorimetric method. Hoechst staining and flow cytometry were used to confirm apoptosis. The data were statistically analyzed using one-way analysis of variance (ANOVA) and independent-samples t-test.

Results

Compared to the control group, we observed a significant increase in the expression levels of the Bax and P53 genes and the activity levels of caspase-3 and 9, and a significant decrease in the expression level of the Bcl-2 gene in MCF-7 and MG-63 treated with effective concentration of progesterone. The caspase-8 activity level did not change significantly in treated MG-63 but increased in treated MCF-7 cells. Hoechst staining and flow cytometry results confirmed apoptosis in the cells exposed to effective concentration of progesterone.

Conclusions

The cytotoxic effect of progesterone on breast cancer and osteosarcoma cells was mediated by apoptotic pathways. In this context, progesterone triggers the extrinsic and intrinsic apoptotic pathways in MCF-7 cells and induces the intrinsic apoptotic pathway in MG-63 cells.

Synchronous papillary thyroid carcinoma and breast ductal carcinoma

A 48-year-old woman was admitted to our hospital with a lump in her left breast. She was diagnosed with synchronous papillary thyroid carcinoma and breast ductal carcinoma. The patient underwent four cycles of neoadjuvant chemotherapy with epirubicin and cyclophosphamide, and one cycle of docetaxel. She then underwent left breast mastectomy and radical resection of thyroid cancer (total thyroidectomy and bilateral central group [levels VI and VII] lymph node dissection) at the same time. She was administered three cycles of chemotherapy with docetaxel and radiotherapy. The patient had no metastasis in the follow-up period. A literature search was performed to characterize the epidemiology, etiology, management, and prognosis of this condition. We speculate that hormone treatment could be a probable pathogenesis of synchronous breast and thyroid cancers.

Shining a Light on the Effects of the Combination of (-)-Epigallocatechin-3-gallate and Tapentadol on the Growth of Human Triple-negative Breast Cancer Cells

BACKGROUND/AIM

Breast cancer is characterized by a high rate of mortality and is considered one of the deadliest types of cancer. It is of note that (-)-epigallocatechin-3-gallate (EGCG), the principal catechin of green tea, is able to hinder the growth of MDA-MB-231 breast cancer cells by influencing different signaling pathways, including apoptosis. Furthermore, EGCG is also used in the treatment of bone cancer pain. Tapentadol, an opioid drug acting at the level of noradrenaline (norepinephrine) reuptake inhibition and μ-opioid receptor, is able to modulate bone cancer pain and influence cancer cell viability by regulating apoptosis.

MATERIALS AND METHODS

In vitro assays were performed on triple-negative MDA-MB-231 cells treated with tapentadol (1, 5, 10, 20, 40 and 80 μg/ml) and EGCG (1, 10, 20, 40, 80, 160 μmol/l), alone and in combination. The effects of EGCG and TAP on viability were determined by wound-healing and MTT assays, while cell migration was assessed by transwell migration.

RESULTS

Cell proliferation, viability and apoptosis of MDA-MB-231 cells were impaired by the combination of EGCG and tapentadol. Specifically, our data show that EGCG and TAP reduced the proliferation of MDA-MB-231 cells by impairing cell-cycle progression (p<0.05). These findings suggest that the combination of these substances may represent a new strategy for the treatment of patients suffering from triple-negative breast cancer.

Single CpG site methylation controls estrogen receptor gene transcription and correlates with hormone therapy resistance

Hormone therapy is the most effective treatment for patients with estrogen receptor α-positive breast cancers. However, although resistance occurs during treatment in some cases and often reflects changed estrogen receptor α status, the relationship between changes in estrogen receptor α expression and resistance to therapy are poorly understood. In this study, we identified a mechanism for altered estrogen receptor α expression during disease progression and acquired hormone therapy resistance in aromatase inhibitor-resistant breast cancer cell lines. Subsequently, we investigated promoter switching and DNA methylation status of the estrogen receptor α promoter, and found marked changes of methylation at a single CpG site (CpG4) in resistant cells. In addition, luciferase reporter assays showed reduced transcriptional activity from this methylated CpG site. This CpG region was also completely conserved among species, suggesting that it acts as a methylation-sensitive Ets-2 transcription factor binding site, as confirmed using chromatin immunoprecipitation assays. In estrogen receptor α-positive tumors, CpG4 methylation levels were inversely correlated with estrogen receptor α expression status, suggesting that single CpG site plays an important role in the regulation of estrogen receptor α transcription.

Epigallocatechin gallate inhibits the growth of MDA-MB-231 breast cancer cells via inactivation of the β-catenin signaling pathway

Epigallocatechin gallate (EGCG), a major constituent of green tea, has potential as a treatment for a variety of diseases, including cancer. EGCG induces apoptosis and inhibits tumorigenesis through multiple signaling pathways in breast cancer cells. β-catenin signaling modulators could be useful in the prevention and therapy of breast cancer. However, the precise anticancer effect of EGCG through the β-catenin signaling pathway in breast cancer is unclear. The present study investigated the association between β-catenin expression and clinicopathological factors of breast cancer patients, and the effect of EGCG on β-catenin expression in breast cancer cells. β-catenin expression was analyzed according to the clinicopathological factors of 74 patients with breast cancer. All patients were females diagnosed with invasive ductal carcinoma. Western blot analysis revealed that β-catenin was expressed at higher levels in breast cancer tissue than in normal tissue. β-catenin expression was associated with lymph node metastasis (P=0.04), tumor-node-metastasis stage (P=0.03) and estrogen receptor status (P<0.01). EGCG decreased MDA-MB-231 cell viability and significantly downregulated the expression of β-catenin, phosphorylated Akt and cyclin D1. Remarkably, additive effects of LY294002 and wortmannin, two phosphatidylinositol-3 kinase inhibitors, were observed. The present results suggest that EGCG inhibits the growth of MDA-MB-231 cells through the inactivation of the β-catenin signaling pathway. Based on these promising results, EGCG may be a potential treatment for triple negative breast cancer patients.

Lack of effect of the procarcinogenic 17β-estradiol on nutrient uptake by the MCF-7 breast cancer cell line

Breast cancer is one of the most frequent cancers in the population, especially in older women. Estrogen is known to be a key hormone in the development and progression of mammary carcinogenesis. In this study, we investigated if the procarcinogenic effect of 17β-estradiol (E2) in breast cancer MCF-7 cells is dependent on changes in glucose or folic acid cellular uptake. The effect of E2 on uptake of ³H-deoxy-d-glucose, ³H-folic acid, cell proliferation (3-thymidine incorporation assay), culture growth (sulforhodamine B assay), viability (lactate dehydrogenase activity assay), lactate production and migration capacity (injury assay) was evaluated. E2 (48h; 100nM) increased culture growth (16%), proliferation rate (24%), cellular viability (36%) and lactate production (38%). In contrast, E2 did not significantly affect the migration capacity of MCF-7 cells. The pro-proliferative, but not the cytoprotective effect of E2 was found to be ERβ-dependent. The polyphenols rutin and caffeic acid were not able to counteract the effect of E2 upon cell proliferation and viability. Uptake of ³H-deoxy-d-glucose was not affected by E2, either in the absence or presence of GLUT inhibitors (cytochalasin B plus phloridzin). Moreover, E2 did not change GLUT1 mRNA levels. Finally, ³H-folic acid uptake was also not affected by E2, both in the absence and presence of the RFC1 inhibitor, methotrexate. The pro-proliferative and cytoprotective effects of E2 are not dependent neither of stimulation of glucose cellular uptake (both GLUT and non-GLUT-mediated) nor of stimulation of folic acid uptake (both RFC1-and non-RFC1-mediated).

Circadian disruption and breast cancer: an epigenetic link?

Breast cancer is already the most common malignancy affecting women worldwide, and evidence is mounting that breast cancer induced by circadian disruption (CD) is a warranted concern. Numerous studies have investigated various aspects of the circadian clock in relation to breast cancer, and evidence from these studies indicates that melatonin and the core clock genes can play a crucial role in breast cancer development. Even though epigenetics has been increasingly recognized as a key player in the etiology of breast cancer and linked to circadian rhythms, and there is evidence of overlap between epigenetic deregulation and breast cancer induced by circadian disruption, only a handful of studies have directly investigated the role of epigenetics in CD-induced breast cancer. This review explores the circadian clock and breast cancer, and the growing role of epigenetics in breast cancer development and circadian rhythms. We also summarize the current knowledge and next steps for the investigation of the epigenetic link in CD-induced breast cancer.

Short-time QiBaoMeiRan Formula Treatment Exerts Estrogenic Activities without Side Effects on Reproductive Tissues in Immature Mice

The Chinese herbal preparation QiBaoMeiRan formula (QBMR) displayed estrogenic effects in ovariectomized rats after long-term administration in a previous study. The uterus and vagina are negatively influenced by estrogens in hormone therapy. While QBMR is known to be a phytoestrogen, its estrogenic effects and safety on reproductive tissues after short-term administration and its mechanism via estrogen receptor (ER) pathway haven’t been studied. Here, we characterized its estrogenic effects using immature mice together with in vitro studies for further molecular characterization. Immature mice were treated with QBMR at doses of 1.125, 2.25, and 4.5 g/kg for 7 days. 1.125 and 2.25 g/kg QBMR promoted the growth and development of uterus and vagina, and upregulated ERα and ERβ expression in reproductive tissues. QBMR had a stimulatory effect on proliferating cell nuclear antigen in vagina but not in uterus, and was without any influence on ki-67 antigen in uterus and vagina. QBMR significantly induced luciferase expression from the ERα/β-estrogen response element (ERE) luciferase reporter and upregulated ERα and ERβ expressions in MCF-7 cells, which were significantly inhibited by estrogen antagonist ICI182,780. This study demonstrated QBMR exerts estrogenic effects on reproductive tissues without side effects and through ER-ERE-dependent pathway.

Synthesis and investigation of biological properties of modified 6-oxa-estra-1,3,5(10),8(9)-tetraenes

To investigate the relationship between structure and biological activity of analogues of steroid estrogens we have developed the synthesis of 7α-methyl-6-oxa-estra-1,3,5(10),8(9)-tetraenes with cis- and trans-junction of C and D rings. We found that such compounds have stronger osteoprotective, cholesterol-lowering and antioxidant properties in comparison with uterotrophic activity; that is the advantage in comparison with clinically used 17α-ethynylestradiol.

Potential activity of fevicordin-A from Phaleria macrocarpa (Scheff) Boerl. seeds as estrogen receptor antagonist based on cytotoxicity and molecular modelling studies

Fevicordin-A (FevA) isolated from Phaleria macrocarpa (Scheff) Boerl. seeds was evaluated for its potential anticancer activity by in vitro and in silico approaches. Cytotoxicity studies indicated that FevA was selective against cell lines of human breast adenocarcinoma (MCF-7) with an IC₅₀ value of 6.4 μM. At 11.2 μM, FevA resulted in 76.8% cell death of T-47D human breast cancer cell lines. Critical pharmacophore features amongst human Estrogen Receptor-α (hERα) antagonists were conserved in FevA with regard to a hypothesis that they could make notable contributions to its pharmacological activity. The binding stability as well as the dynamic behavior of FevA towards the hERα receptor in agonist and antagonist binding sites were probed using molecular dynamics (MD) simulation approach. Analysis of MD simulation suggested that the tail of FevA was accountable for the repulsion of the C-terminal of Helix-11 (H11) in both agonist and antagonist receptor forms. The flexibility of loop-534 indicated the ability to disrupt the hydrogen bond zipper network between H3 and H11 in hERα. In addition, MM/GBSA calculation from the molecular dynamic simulations also revealed a stronger binding affinity of FevA in antagonistic action as compared to that of agonistic action. Collectively, both the experimental and computational results indicated that FevA has potential as a candidate for an anticancer agent, which is worth promoting for further preclinical evaluation.

Mouse models of BRCA1 and their application to breast cancer research

Germline mutations of human breast cancer-associated gene 1 (BRCA1) predispose women to breast and ovarian cancers. In mice, over 20 distinct mutations, including null, hypomorphic, isoform, conditional, and point mutations, have been created to study functions of Brca1 in mammary development and tumorigenesis. Analyses using these mutant mice have yielded an enormous amount of information that greatly facilitates our understanding of the gender- and tissue-specific tumor suppressor functions of BRCA1, as well as enriches our insights into applying these preclinical models of disease to breast cancer research. Here, we review features of these mutant mice and their applications to cancer prevention and therapeutic treatment.

Homeobox A7 stimulates breast cancer cell proliferation by up-regulating estrogen receptor-alpha

Breast cancer is the most common hormone-dependent malignancy in women. Homeobox (HOX) transcription factors regulate many cellular functions, including cell migration, proliferation and differentiation. The aberrant expression of HOX genes has been reported to be associated with human reproductive cancers. Estradiol (E2) and its nuclear receptors, estrogen receptor (ER)-alpha and ER-beta, are known to play critical roles in the regulation of breast cancer cell growth. However, an understanding of the potential relationship between HOXA7 and ER in breast cancer cells is limited. In this study, our results demonstrate that knockdown of HOXA7 in MCF7 cells significantly decreased cell proliferation and ERα expression. In addition, HOXA7 knockdown attenuated E2-induced cell proliferation as well as progesterone receptor (PR) expression. The stimulatory effects of E2 on cell proliferation and PR expression were abolished by co-treatment with ICI 182780, a selective ERα antagonist. In contrast, overexpression of HOXA7 significantly stimulated cell proliferation and ERα expression. Moreover, E2-induced cell proliferation, as well as PR expression, was enhanced by the overexpression of HOXA7. Neither knockdown nor overexpression of HOXA7 affected the ER-beta levels. Our results demonstrate a novel mechanistic role for HOXA7 in modulating breast cancer cell proliferation via regulation of ERα expression. This finding contributes to our understanding of the role HOXA7 plays in regulating the proliferation of ER-positive cancer cells.

Thioredoxin-mediated redox regulation of resistance to endocrine therapy in breast cancer

Resistance to endocrine therapy in breast carcinogenesis due to the redox regulation of the signal transduction system by reactive oxygen species (ROS) is the subject of this review article. Both antiestrogens and aromatase inhibitors are thought to prevent cancer through modulating the estrogen receptor function, but other mechanisms cannot be ruled out as these compounds also block metabolism and redox cycling of estrogen and are free radical scavengers. Endocrine therapeutic agents, such as, tamoxifen and other antiestrogens, and the aromatase inhibitor, exemestane, are capable of producing ROS. Aggressive breast cancer cells have high oxidative stress and chronic treatment with exemestane, fulvestrant or tamoxifen may add additional ROS stress. Breast cancer cells receiving long-term antiestrogen treatment appear to adapt to this increased persistent level of ROS. This, in turn, may lead to the disruption of reversible redox signaling that involves redox-sensitive phosphatases, protein kinases, such as, ERK and AKT, and transcription factors, such as, AP-1, NRF-1 and NF-κB. Thioredoxin modulates the expression of estrogen responsive genes through modulating the production of H2O2 in breast cancer cells. Overexpressing thioredoxine reductase 2 and reducing oxidized thioredoxin restores tamoxifen sensitivity to previously resistant breast cancer cells. In summary, it appears that resistance to endocrine therapy may be mediated, in part, by ROS-mediated dysregulation of both estrogen-dependent and estrogen-independent redox-sensitive signaling pathways. Further studies are needed to define the mechanism of action of thioredoxin modifiers, and their effect on the redox regulation that contributes to restoring the antiestrogen-mediated signal transduction system and growth inhibitory action.

Epigenetic reactivation of estrogen receptor-α (ERα) by genistein enhances hormonal therapy sensitivity in ERα-negative breast cancer

BACKGROUND

Estrogen receptor-α (ERα)-negative breast cancer is clinically aggressive and normally does not respond to conventional estrogen target-directed therapies. The soybean isoflavone, genistein (GE), has been shown to prevent and inhibit breast cancer and recent studies have suggested that GE can enhance the anticancer capacity of an estrogen antagonist, tamoxifen (TAM), especially in ERα-positive breast cancer cells. However, the role of GE in ERα-negative breast cancer remains unknown.

METHODS

We have evaluated the in vitro and in vivo epigenetic effects of GE on ERα reactivation by using MTT assay, real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, western-blot assay, immunoprecipitation (ChIP) assay, immunohistochemistry and epigenetic enzymatic activity analysis. Preclinical mouse models including xenograft and spontaneous breast cancer mouse models were used to test the efficacy of GE in vivo.

RESULTS

We found that GE can reactivate ERα expression and this effect was synergistically enhanced when combined with a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), in ERα-negative MDA-MB-231 breast cancer cells. GE treatment also re-sensitized ERα-dependent cellular responses to activator 17β-estradiol (E2) and antagonist TAM. Further studies revealed that GE can lead to remodeling of the chromatin structure in the ERα promoter thereby contributing to ERα reactivation. Consistently, dietary GE significantly prevented cancer development and reduced the growth of ERα-negative mouse breast tumors. Dietary GE further enhanced TAM-induced anti-cancer efficacy due at least in part to epigenetic ERα reactivation.

CONCLUSIONS

Our studies suggest that soybean genistein can epigenetically restore ERα expression, which in turn increases TAM-dependent anti-estrogen therapeutic sensitivity in vitro and in vivo. The results from our studies reveal a novel therapeutic combination approach using bioactive soybean product and anti-hormone therapy in refractory ERα-negative breast cancer which will provide more effective options in breast cancer therapy.

Polymorphisms of Phase I and Phase II Enzymes and Breast Cancer Risk

Breast cancer is a complex disease which is provoked by a multitude of exogenous and endogenous factors including genetic variations. Recent genome-wide association studies identified a set of more than 18 novel low penetrant susceptibility loci, however, a limitation of this powerful approach is the hampered analysis of polymorphisms in DNA sequences with a high degree of similarity to other genes or pseudo genes. Since this common feature affects the majority of the highly polymorphic genes encoding phase I and II enzymes the retrieval of specific genotype data requires adapted amplification methods. With regard to breast cancer these genes are of certain interest due to their involvement in the metabolism of carcinogens like exogenous genotoxic compounds or steroid hormones. The present review summarizes the observed effects of functional genetic variants of phase I and II enzymes in well designed case control studies to shed light on their contribution to breast cancer risk.

Synergistic epigenetic reactivation of estrogen receptor-α (ERα) by combined green tea polyphenol and histone deacetylase inhibitor in ERα-negative breast cancer cells

Background

The status of estrogen receptor-α (ERα) is critical to the clinical prognosis and therapeutic approach in breast cancer. ERα-negative breast cancer is clinically aggressive and has a poor prognosis because of the lack of hormone target-directed therapies. Previous studies have shown that epigenetic regulation plays a major role in ERα silencing in human breast cancer cells. Dietary green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), is believed to be an anticancer agent in part through its regulation of epigenetic processes.

Results

In our current studies, we found that EGCG can reactivate ERα expression in ERα-negative MDA-MB-231 breast cancer cells. Combination studies using EGCG with the histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), revealed a synergistic effect of reactivation of ERα expression in ERα-negative breast cancer cells. Reactivation of ERα expression by EGCG and TSA treatment was found to sensitize ERα-dependent cellular responses to activator 17β-estradiol (E₂) and antagonist tamoxifen in ERα-negative breast cancer cells. We also found that EGCG can lead to remodeling of the chromatin structure of the ERα promoter by altering histone acetylation and methylation status thereby resulting in ERα reactivation. A decreased binding of the transcription repressor complex, Rb/p130-E2F4/5-HDAC1-SUV39H1-DNMT1, in the regulatory region of the ERα promoter also contributes to ERα transcriptional activation through treatment with EGCG and/or TSA.

Conclusions

Collectively, these studies show that green tea EGCG can restore ERα expression by regulating epigenetic mechanisms, and this effect is enhanced when combined with an HDAC inhibitor. This study will facilitate more effective uses of combination approaches in breast cancer therapy and will help to explore more effective chemotherapeutic strategies toward hormone-resistant breast cancer.

Gynaecologic challenging issues in the management of BRCA mutation carriers: oral contraceptives, prophylactic salpingo-oophorectomy and hormone replacement therapy

BRCA1 and BRCA2 mutation carriers have a 54-85% and 45% lifetime risk of developing breast cancer, respectively, and a 18-60% and 11-27% lifetime risk of developing ovarian cancer, respectively. Oral contraceptives (OCs) significantly reduce the risk of ovarian cancer also in BRCA1/BRCA2 mutation carriers. The association between OC use and breast cancer risk in these women is controversial. Some studies showed a modestly increased risk especially among BRCA1 mutation carriers. The risk appears to be greater for women who took OCs for at least 5 years and who took OCs before the age of 30 years. Other studies reported that duration of use before first full-term pregnancy has a positive association with breast cancer risk. Salpingo-oophorectomy reduces the risk of coelomic epithelial cancer of 80-95% and the risk of breast cancer of approximately 50%. BRCA1 and BRCA2 mutation carriers should be encouraged to undergo prophylactic bilateral salpingo-oophorectomy at the age of 35-40 years or when childbearing is complete. Short-term use of hormone replacement therapy may relieve menopausal symptoms and does not appear to affect the breast cancer risk reduction obtained with salpingo-oophorectomy.

Progestagen component in combined hormone replacement therapy in postmenopausal women and breast cancer risk: a debated clinical issue

The relevance of the progestagen component in combined hormone replacement therapy (HRT) for breast cancer risk has been long debated. In vitro studies have shown that progestins exert both genomic transcriptional and non-genomic effects that can enhance the proliferation, invasiveness and spread of breast cancer cells. According to a novel hypothesis, progestins can still activate cancer stem cells in patients with pre-existing, clinically undetected breast cancer. However, some experimental and clinical data suggest that different progestins may have a different impact on the pathophysiology of malignant breast cells. In vitro studies on estrogen receptor (ER)+ breast cancer cells have shown that the addition of medroxyprogesterone acetate (MPA) to estradiol (E(2)) produces a significantly higher increase of the mRNA levels and activities of estrogen-activating enzymes aromatase, 17beta hydroxysteroid dehydrogenase type-1 and sulfatase when compared with progesterone plus E(2). In randomised trial performed on ovariectomised adult female monkeys, oral E(2) plus MPA have resulted in a significantly greater proliferation of breast lobular and ductal epithelium when compared with placebo, whereas E(2) plus micronised progesterone have not. In the same experimental model, oral E(2) plus MPA have been found to induce the expression of genes encoding epidermal growth factor receptor (EGFR) ligands and downstream targets, whereas E(2) alone or E(2) plus micronised progesterone had no or modest effects on EGFR-related genes. In last years, some clinical studies on HRT users have shown that androgenic progestin- or MPA-based formulations are associated with an increased breast cancer incidence, whereas micronised progesterone- or dydrogesterone-based formulations are not. Further basic and clinical investigations on this topic are strongly warranted to elucidate whether the choice of the progestagen component in combined HRT could be of clinical relevance as for breast cancer risk.

Xenoestrogens may be the cause of high and increasing rates of hormone receptor positive breast cancer in the world

Breast cancer rates are higher in the Western or industrialized world when compared to Africa or Asia. Within the developing world, breast cancer rates are higher in urban areas where people have a more Westernized lifestyle. In addition, there has been a steady increase in the breast cancer incidence across the world. It is already a known fact that the proportion of hormone receptor positive breast cancer cases is higher in the developed world. Evidence from developed countries also shows that most of the increase in breast cancer incidence has been due to an increase in hormone receptor positive breast cancer. Most of the breast cancer incidence can be explained by environmental factors and genetic causes. However, all known risk factors of breast cancer can explain only 30-50% of breast cancer incidence. In the past decade, a number of compounds that affect female hormone homeostasis have been discovered. These xenoestrogens have been shown to cause breast cancer and also induce the expression of hormone receptors in vitro and in vivo. Given the high use of substances containing xenoestrogens in developed regions of the world and their increasing use in urban parts of the developing world, xenoestrogens could be the important cause of high and increasing rates of hormone receptor positive breast cancer across the world. New research in the area of mammary stem cells provides added indication of the probable time period of exposure to xenoestrogens with chronic exposure later in life leading to hormone receptor positive breast cancer and most probable reason behind increasing breast cancer incidence.

Wilms' tumor 1 suppressor gene mediates antiestrogen resistance via down-regulation of estrogen receptor-alpha expression in breast cancer cells

The antiestrogen tamoxifen has been used in the treatment of hormone-responsive breast cancer for over a decade. The loss of estrogen receptor (ER) expression is the most common mechanism for de novo antiestrogen resistance. Wilms' tumor 1 suppressor gene (WT1) is a clinically useful marker that is associated with poor prognosis in breast cancer patients; its high level expression is frequently observed in cases of breast cancer that are estrogen and progesterone receptor negative. The lack of expression of these receptors is characteristic of tumor cells that are not responsive to hormonal manipulation. To determine whether there is a linkage between WT1 expression and antiestrogen resistance in breast cancer cells, we studied the effect of WT1 on tamoxifen responsiveness in ERalpha-positive MCF-7 cells. We found that overexpression of WT1 in MCF-7 markedly abrogated tamoxifen-induced cell apoptosis and 17beta-estradiol (E(2))-mediated cell proliferation. The expressions of ERalpha and its downstream target genes were significantly repressed following overexpression of WT1, whereas the down-regulation of WT1 by WT1 shRNA could enhance ERalpha expression and the sensitivity to tamoxifen treatment in ERalpha-negative MDA468 and HCC1954 cells that express high levels of WT1. Furthermore, we have confirmed that the WT1 protein can bind to endogenous WT1 consensus sites in the proximal promoter of ERalpha and thus inhibit the transcriptional activity of the ERalpha promoter in a WT1 site sequence-specific manner. Our study clearly implicates WT1 as a mediator of antiestrogen resistance in breast cancer through down-regulation of ERalpha expression and supports the development of WT1 inhibitors as a potential means of restoring antiestrogen responsiveness in breast cancer therapy.

Effects of chronic genistein treatment in mammary gland, uterus, and vagina

BACKGROUND

The isoflavone genistein (GEN) is found in soy (Glycine max) and red clover (Trifolium pratense). The estrogenic activity of GEN is known, and it is widely advertised as a phytoestrogen useful in alleviating climacteric complaints and other postmenopausal disorders. Knowledge of effects of long-term administration of GEN in laboratory animals is scarce, and effects in the uterus and mammary gland after long-term administration have not been studied. The uterus and mammary gland are known to be negatively influenced by estrogens used in hormone therapy.

OBJECTIVES

We administered two doses of GEN [mean daily uptake 5.4 (low) or 54 mg/kg (high) body weight (bw)] orally over a period of 3 months to ovariectomized (ovx) rats and compared the effects with a treatment with two doses of 17beta-estradiol [E(2); 0.17 (low) or 0.7 mg/kg bw (high)]. Mammary glands, vaginae, and uteri were investigated morphologically and immunohistochemically. We quantified the expression of proliferating cell nuclear antigen (PCNA) and progesterone receptor (PR) in the mammary gland.

RESULTS

In rats treated with either of the E(2) doses or the high GEN dose, we found increased uterine weight, and histologic analysis showed estrogen-induced features in the uteri. In vaginae, either E(2) dose or GEN high induced hyperplastic epithelium compared with the atrophic controls. In the mammary gland, E(2) (either dose) or GEN increased proliferation and PR expression. Serum levels of luteinizing hormone were decreased by E(2) (both doses) but not by GEN.

CONCLUSIONS

In summary, E(2) and GEN share many effects in the studied organs, particularly in the vagina, uterus, and mammary gland but not in the hypothalamo/pituitary unit.

Effects of voluntary wheel running on cardiac function and myosin heavy chain in chemically gonadectomized rats

Reducing testosterone and estrogen levels with a luteinizing hormone-releasing hormone agonist such as Zoladex (i.e., chemical gonadectomy) is a common treatment for many prostate and breast cancer patients, respectively. There are reports of surgical gonadectomy inducing cardiac dysfunction, and exercise has been shown to be cardioprotective under these circumstances. Minimal research has been done investigating the effects of chemical gonadectomy and increased physical activity on cardiac function. The purpose of this investigation was to examine the effects of chemical gonadectomy and physical activity on cardiac function. Male (M) and female (F) Sprague-Dawley rats received either Zoladex treatment (Zol) that suppressed gonadal function for 8 wk or control implants (Con) and either were allowed unlimited access to voluntary running wheels (WR) or remained sedentary (Sed) throughout the treatment period. In vivo and ex vivo left ventricle (LV) function were then assessed, and myosin heavy chain (MHC) expression was analyzed to help explain LV functional differences. Hearts from M Sed+Zol exhibited significantly lower aortic blood flow velocity, developed pressure, and maximal rate of pressure development and higher beta-MHC expression than M Sed+Con. Hearts from F Sed+Zol exhibited significantly lower LV wall thicknesses, fractional shortening, and developed pressure and higher beta-MHC expression than F Sed+Con. This cardiac dysfunction was not evident in hearts from M or F WR+Zol, and this was associated with a preservation of the MHC isoform distribution. Thus an 8-wk chemical gonadectomy with Zoladex promoted cardiac dysfunction in male and female rats, and voluntary wheel running protected against this cardiac dysfunction.

[Synthesis, structure, and biological properties of some 8alpha-analogues of steroid estrogens with fluorine in position 2]

A total synthesis of 8alpha analogues of steroid estrogens with fluorine in position 2 was achieved. Structural features of these compounds were studied by the example of 17beta-acetoxy-2-fluoro-3-methoxy-8alpha-estra-1,3,5(10)-triene. It was shown that the 8alpha analogues of 2-fluorosubstituted steroid estrogens have a low uterotropic activity and retain the osteoprotective and hypocholesterolemic activities.

COUP-TFI modulates estrogen signaling and influences proliferation, survival and migration of breast cancer cells

We previously showed that COUP-TFI interacts with the Estrogen Receptor alpha (ER alpha) to recruit Extracellular signal Regulated Kinases (ERKs) in an Estradiol (E2)-independent manner, resulting in an enhancement of ER alpha transcriptional activity. However, the involvement of COUP-TFI in physiologically relevant functions of ER alpha, such as the mitogenic activity that E2 has on breast cancer cells, remains poorly understood. Here, we first showed that the amounts of COUP-TFI protein are higher in dedifferentiated mammary cell lines (MDA-MB-231) and tumor breast cells as compared to the differentiated MCF-7 cell line and normal breast cells. To evaluate the functional relevance of the COUP-TFI/ER alpha interplay in mammary cells, we generated MCF-7 cells that stably over-express COUP-TFI. We found that the over-expression of COUP-TFI enhances motility and invasiveness of MCF-7 cells. COUP-TFI also promotes the proliferation of MCF-7 cells through ER alpha-dependent mechanisms that target cell cycle progression and cell survival. To further investigate the mechanisms underlying these effects of COUP-TFI, we evaluated the expression of known E2-target genes in breast cancer, and found that COUP-TFI differentially regulated genes involved in cell proliferation, apoptosis, and migration/invasion. Notably, Cathepsin D (CTSD) transcript and protein levels were significantly higher in presence and absence of E2 in MCF-7 over-expressing COUP-TFI. Chromatin Immunoprecipitation assays showed that ER alpha, phospho-RNA Polymerase II, as well as p68 RNA Helicase, a phospho-Serine 118 dependent co-activator of ER alpha, were preferentially recruited onto the CTSD gene proximal promoter in COUP-TFI over-expressing cells. These results suggest that COUP-TFI selectively regulates the expression of endogenous E2-target genes and consequently modifies ER alpha positive mammary cells response to E2.

A role of estrogen/ERalpha signaling in BRCA1-associated tissue-specific tumor formation

Estrogen and its receptor alpha (ERalpha) have been implicated in the tissue-specific tumorigenesis associated with BRCA1 mutations. However, the majority of breast cancers developed in human BRCA1 mutation carriers are ERalpha-negative, challenging the link between BRCA1 and estrogen/ERalpha in breast cancer formation. Using a mouse model lacking the full-length form of BRCA1, here we show that ERalpha is highly expressed in the premalignant mammary gland and initiation stages of tumorigenesis, although its expression is gradually diminished during mammary tumor progression. We demonstrate that the absence of full-length BRCA1 increases sensitivity of cells to estrogen-induced extracellular signal-regulated kinase 1/2 phosphorylation and cyclin D1 expression. The absence of BRCA1 turns the proliferation of ERalpha-positive cells from a paracrine fashion to an autocrine or endocrine fashion. Consequently, BRCA1-mutant cells are sensitized to estrogen-induced cell proliferation in vitro and mammary tumorigenesis in vivo. These findings illustrate a molecular mechanism for estrogen/ERalpha signals in BRCA1-associated tissue-specific tumor formation, and identify several key elements in the estrogen/ERalpha-signaling cascade that can serve as potential therapeutic targets for BRCA1-associated tumorigenesis.

Analysis of population characteristics related to the total effective xenoestrogen burden: A biomarker of xenoestrogen exposure in breast cancer

To analyse the link between breast cancer and the combined effect of environmental xenoestrogens, we developed, standardised and applied a biomarker of exposure to assess the total effective xenoestrogen burden (TEXB) in human adipose tissue in a case-control study. Environmental oestrogens (TEXB-alpha) are separated from endogenous oestrogens (TEXB-beta), and the combined oestrogenic effect is determined from its proliferative effect (E-Screen assay). The aim of the study was to identify potential confounders, effect modifiers or other covariates associated with higher TEXB levels. In cases, age, family history of breast cancer, lactation experience and smoking were associated with TEXB-alpha. In controls, only age was associated with TEXB-alpha levels. In cases, age, educational level, age at menarche, menopausal status, marital status, lactation experience and smoking were associated with TEXB-beta. In controls, only menopausal status was significantly associated with TEXB-beta levels. In conclusion, TEXB, as a biomarker of exposure, takes account of environmental, dietary, lifestyle, genetic and reproductive factors, which are not usually systematically measured across studies.

Biomonitoring of environmental estrogens in human tissues

Two examples are presented for the application of the total effective xenoestrogen burden as biomarker of chemical exposure measured in tissue samples from patients recruited for two case-control studies. The first study focused on environmental chemicals with hormone mimicking activity, the so-called environmental estrogens, and their participation in the etiology of breast cancer. The second study investigated mother-child exposure to persistent organochlorine chemicals and assessed their combined effect on the risk of male urogenital malformations in the newborn.

Chemoprevention of breast cancer among Asian women--its perspective and problems

Chemoprevention of breast cancer employing tamoxifen and others has been demonstrated to be effective in reducing the frequency of developing breast malignancy in Western countries. In Asian countries, the frequency of breast cancer as well as its premalignant lesions has recently increased. Therefore, the possible chemoprevention may benefit those women with potential high risks of developing breast cancer and with premalignant lesions. However, the details of these findings of chemoprevention in Western countries have not been available for women with Asian descendant. In addition, risk factors of developing breast cancer in healthy women have not been established in Asian countries compared to Western countries with relative paucity of familial breast cancer cases. Thus, possible chemoprevention of breast cancer in Asian countries may be targeted toward those with established premalignant breast lesions such as ductal carcinoma in situ and/or atypical ductal hyperplasia. However, due to their recent increment of their incidence, biological and/or clinical features of these premalignant breast lesions have not been extensively characterized in Asian women and further investigations are required for wide spread chemoprevention.

Overexpression of aurora kinase A in mouse mammary epithelium induces genetic instability preceding mammary tumor formation

Aurora-A/STK15/BTAK, which encodes a centrosome-associated kinase, is amplified and overexpressed in multiple types of human tumors, including breast cancer. However, the causal relationship between overexpression of Aurora-A and tumorigenesis has not been fully established due to contradictory data obtained from different experimental systems. To investigate this, we generated a mouse strain that carries an MMTV-Aurora-A transgene. We showed that all the MMTV-Aurora-A mice displayed enhanced branch morphogenesis in the mammary gland and about 40% developed mammary tumors at 20 months of age. The tumor incidence was significantly increased in a p53(+/-) mutation background with about 70% MMTV-Aurora-A;p53(+/-) animals developed tumors at 18 months of age. Of note, overexpression of Aurora-A led to genetic instability, characterized by centrosome amplification, chromosome tetraploidization and premature sister chromatid segregation, at stages prior to tumor formation. Most notably, the severe chromosomal abnormality did not cause cell death owing to the activation of AKT pathway, including elevated levels of phosphorylated AKT and mammalian target of rapamycin, and nuclear accumulation of cyclin D1, which enabled continuous proliferation of the tetraploid cells. These data establish Aurora-A as an oncogene that causes malignant transformation through inducing genetic instability and activating oncogenic pathways such as AKT and its downstream signaling.

NFAT induces breast cancer cell invasion by promoting the induction of cyclooxygenase-2

The NFAT (nuclear factor of activated T cells) family of transcription factors plays a fundamental role in the transcriptional regulation of the immune response. However, NFATs are ubiquitously expressed, and recent evidence points to their important functions in human epithelial cells and carcinomas. Specifically, NFAT has been shown to be active in human breast and colon carcinoma cells and to promote their invasion through Matrigel. The mechanisms by which NFAT promotes invasion have not been defined. To identify NFAT target genes that induce carcinoma invasion, we have established stable breast cancer cell lines that inducibly express transcriptionally active NFAT. Gene expression profiling by cDNA microarray of cells induced to express NFAT revealed up-regulation of cyclooxygenase-2 (COX-2). Increased NFAT expression and activity induced COX-2 expression as well as prostaglandin E2 synthesis. This induction was more prominent when NFAT was activated by phorbol 12-myristate 13-acetate and calcium ionophore ionomycin and was blocked by the NFAT antagonist cyclosporin A. Breast cancer cells with elevated COX-2 expression showed increased invasion through Matrigel, and this was reduced in cells treated with COX-2 inhibitors. Conversely, loss of NFAT1 protein expression using small interfering RNA led to a reduction in COX-2 transcription and reduced invasion. Similarly, Matrigel invasion was reduced in cells in which COX-2 expression was reduced using specific siRNA. These findings demonstrate that NFAT promotes breast cancer cell invasion through the induction of COX-2 and the synthesis of prostaglandins.

Breast cancer, oestrogens and environmental pollutants: a re-evaluation from a mixture perspective

The continuing rise in breast cancer incidence rates in almost all Western countries cannot be explained entirely in terms of known risk factors of the disease process. Additional determinants need to be examined, among them exposure to environmental pollutants. With the demonstration that elevated levels of endogenous sex hormones and the use of hormones for the relief of menopausal symptoms are associated with the disease, the oestrogen hypothesis of breast cancer has received further empirical support. This has led to heightened concerns about the possible involvement of oestrogen-like pollutants, such as p,p'-Dichlorodiphenyldichloroethane (DDE). Case-control studies assessing whether women with breast cancer have elevated burdens of p,p'-DDE have produced results not suggestive of a link with cancer risks. However, possible effects of p,p'-DDE and other pollutants cannot be seen in isolation from sex hormones also present in serum. In view of the low potency of p,p'-DDE, and its low levels in serum, it seems unlikely that the chemical on its own will add significantly to the action of sex hormones. However, chemical analyses show that numerous pollutants with oestrogen-like effect profiles can be found in human tissues. Thus, the oestrogen hypothesis of breast cancer should be extended to encompass the multitude of these agents. Viewed from such a perspective, a putative role of organochlorines and other agents in breast cancer should not be dismissed prematurely. Instead, breast cancer epidemiology should face the reality of combined exposures and should take account of recent evidence from in vitro models demonstrating that a large number of oestrogen-like pollutants, all present at low levels, can act together to add to the internal oestrogenic load.

Efficacy and safety of 17alpha-hydroxyprogesterone caproate in hormone replacement therapy

The aim of the present study was to evaluate the efficacy (in terms of induction of uterine bleeding) and safety (in terms of absence of endometrial hyperplasia) of 17alpha-hydroxyprogesterone caproate (17alpha-HPC) in a therapeutic regimen for hormonal replacement after menopause. Fifty postmenopausal patients received hormone replacement therapy (HRT) for 24 weeks. The treatment regimen consisted of standard estrogen replacement therapy at commonly prescribed doses for the prevention of climacteric symptoms and 341 mg of 17alpha-HPC every 30 days. Enrolled women were told to expect withdrawal bleeding 7-10 days after the administration of 17alpha-HPC. Forty-eight patients completed the trial. In 91.7% of cases, patients experienced the expected pattern, i.e., strict withdrawal bleeding exclusive of any other form of bleeding. Breakthrough bleeding and/or other forms of abnormal bleeding affected only four women. At the 6th month none of the endometrial samplings motivated by endometrial thickness >10 mm and evidence of heterogeneous echogenicity (two cases) was positive for carcinoma. No biopsies had to be performed at the end of the 12th month of treatment. No serious adverse effect where recorded during the study period. In conclusion, our data show the efficacy and safety of 17alpha-HPC in HRT.